The pledge, made by Andrew Lansley, the shadow health secretary, dismayed some Right-wing Tories and drew attacks from Labour, which accused the opposition of making "wild and rash tax-and-spend pledges".

Mr Lansley signalled in a newspaper interview that a Conservative government would make cuts in the public sector to fund a continued rise in health spending.

His pledge was backed by David Cameron, the Conservative leader. Mr Lansley said rising life expectancy and the cost of medical technology mean spending on health has to rise from about nine per cent of GDP to 11 per cent.

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That would mean another major increase in health spending, on top of the £40 billion spent by Gordon Brown since 2002.

Even Derek Wanless, the architect of Mr Brown's spending surge, has admitted that much of the money spent on the NHS has not led to productivity improvements.

But Mr Cameron's team is convinced that if it is to persuade voters that the Conservatives are the "party of the NHS", they must at least match Labour's health spending plans.

Mr Lansley's plan could even see the Tories spend more than Labour on health. He admitted that boosting health spending would require "tough" cuts in other areas.

"There are places where the future of public expenditure is for it to decline as a proportion of GDP or indeed in some cases in absolute terms," he said.

Privately, some senior Tories are uncomfortable about the strategy, fearing it could hurt the party.

"This shows that everyone has to be careful with what they say or we risk being blown off course," said one shadow cabinet member.

The pledge also added to tensions on the Tory frontbench. Under orders from George Osborne, shadow cabinet members have held back from promising to spend more. Liam Fox, the shadow defence secretary, has been particularly constrained in attacking Labour's defence record because he has been unable to pledge more funds for the Armed Forces.

Yesterday, Labour dispatched public letters to several Tory frontbenchers suggesting that a Conservative government would have to cut spending on defence, education and policing to pay for the increased health expenditure.

Yvette Cooper, the Chief Secretary to the Treasury, said Mr Lansley's pledge showed that "George Osborne has lost control and is allowing the Tory frontbench to make wild and rash tax-and-spend pledges without thinking how they would be paid for".